(Volcano Watch is a weekly article written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.)
Late in the evening on Nov. 13, 1985, most of those living in the Colombian town of Armero, on the shores of the river Lagunillas, were in bed.
The nearby volcano, Nevado del Ruiz, had been quiet for the past couple of months, and the mayor and the town priest had assured the people of Armero that they were safe for the night.
Unfortunately, a storm had been brewing over the area, and the explosive eruption that occurred on the mountain, obscured by rain that night, went unnoticed by Armero residents. Those who experienced the eruption had no way of relaying information quickly and efficiently to Armero, the place most in danger.
Nevado del Ruiz is a stratovolcano, akin to Washington’s Mount St. Helens, topped by glaciers, rising 17,784 feet above sea level. Such volcanoes are especially dangerous, because heat from the eruptions melts the ice to create lahars, or mudflows of volcanic debris. These are not slow, cumbersome mudflows, but fast, deep, and destructive walls of debris and water.
The volcano first began to stir about a year earlier, its reawakening marked by a swarm of earthquakes. Fumarolic activity in the summit crater began around the same time.
A visiting UN geologist advised the installation of monitoring equipment and the creation of a hazard map and evacuation plans. But Colombian scientists lacked the expertise, government support, and equipment necessary to effectively monitor the volcano and relay information to public authorities.
They requested aid—both equipment and scientists—from foreign countries and were sent a few seismographs without proper instructions on how to operate the instruments and analyze the data.
In addition, the Colombian government was preoccupied with civil matters. In Bogota, Colombia’s capital, guerrilla warfare had broken out, and the Colombian President sent troops to quell the rebellion.
To the government, the unstable political situation was more pressing than the volcanic activity. It did not help that the information about threats from Nevada del Ruiz provided to officials by various visiting and Colombian scientists was often contradictory and vague.
A minor explosive eruption Sept. 11 and a calmer political situation refocused officials on volcanic matters. City, county, and federal officials started meeting with scientists to discuss hazard map creation, evacuation plans, and possible eruption times and outcomes.
Progress finally started at the federal and county levels, but the little town of Armero, built on old lahar deposits 28 miles from the volcano, still went mostly unnoticed by government officials.
Before an effective line of communication and evacuation plan could be created, Nevado del Ruiz erupted again and sent lahars racing north and east through the deep river valleys on Nevado del Ruiz’s flanks.
With little warning, the river Lagunillas heaved its muddy contents onto the flatlands, directly into the city of Armero.
Within minutes, 23,000 people — most of the town’s inhabitants — were killed, entombed within a concrete-like mixture of mud, vegetation, buildings, and everything else swept away by the lahars. Sadly, the lahars reached Armero approximately two hours after the eruption — plenty of time for the people to have evacuated to higher ground, had they been notified more quickly.
The 1985 eruption of Colombia’s Nevado del Ruiz is the second most deadly volcanic eruption of the 20th century, resulting in the deaths of more than 25,000 people.
Communities worldwide learned valuable lessons from this calamity. These include proper equipment and training for monitoring scientists to understand and help others understand what is happening.
Effective communication between all parties is one of the most essential components of living around an active volcano. Mount Pinatubo in the Philippines awoke in 1991, the entire volcanological community responded, thus averting a disaster like the Armero tragedy.
Every day, we continue to learn more about the volcanoes of our Earth. Looking back into the past is another way to catch a glimpse of the future.